FIG. 1 is a cross-sectional view, not to scale of a portion of the substrate having the multi-layer coating on its surface.
The article or substrate 18 can be comprised of any suitable material such as plastic, ceramic, metal or metal alloy. The metals include nickel, aluminum, copper, steel and zinc. The metal alloys include nickel alloys and brass. The plastics forming the substrate include polycarbonates, nylon, acrylonitrile-butadiene-styrene, polyesters, polyvinylchlorides, and the like. In one embodiment the article is part of a vehicle, such as for example, a wheel cover.
Over the surface of the substrate 18 is deposited a polymeric or resinous layer 20. The polymeric or resinous layer or basecoat 20 may be comprised of both thermoplastic and thermoset polymeric or resinous material. These polymeric or resinous materials include the well known, conventional and commercially available polycarbonates, polyacrylates, polymethacrylates, nylons, polyesters, polypropylenes, polyepoxies, alkyds and styrene containing polymers such as polystyrene, styrene-acrylonitrile (SAN), styrene-butadiene, acrylonitrile-butadiene-styrene (ABS), and blends and copolymers thereof.
The polycarbonates are described in U.S. Pat. Nos. 4,579,910 and 4,513,037, both of which are incorporated herein by reference.
Nylons are polyamides which can be prepared by the reaction of diamines with dicarboxylic acids. The diamines and dicarboxylic acids which are generally utilized in preparing nylons generally contain from two to about 12 carbon atoms. Nylons can also be prepared by additional polymerization. They are described in xe2x80x9cPolyamide Resinsxe2x80x9d, D. E. Floyd, Reinhold Publishing Corp., New York, 1958, which is incorporated herein by reference.
The polyepoxies are disclosed in xe2x80x9cEpoxy Resinsxe2x80x9d, by H. Lee and K. Neville, McGraw-Hill, New York, 1957, and in U.S. Pat. Nos. 2,633,458; 4,988,572; 4,680,076; 4,933,429 and 4,999,388, all of which are incorporated herein by reference.
The polyesters are polycondensation products of an aromatic dicarboxylic acid and a dihydric alcohol. The aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4xe2x80x2-diphenyl-dicarboxylic acid, 2,6-naphthalenedi-carboxylic acid, and the like. Dihydric alcohols include the lower alkane diols with from two to about 10 carbon atoms such as, for example, ethylene glycol, propylene glycol, cyclohexanedimethanol, and the like. Some illustrative non-limiting examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, and poly(1,4-cyclohexanedimethylene terephthalate). They are disclosed in U.S. Pat. Nos. 2,465,319; 2,901,466 and 3,047,539, all of which are incorporated herein by reference.
The polyacrylates and polymethacrylates are polymers or resins resulting from the polymerization of one or more acrylates such as, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., as well as the methacrylates such as, for instance, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, etc. Copolymers of the above acrylate and methacrylate monomers are also included within the term xe2x80x9cpolyacrylates or polymethacrylatesxe2x80x9d as it appears herein. The polymerization of the monomeric acrylates and methacrylates to provide the polyacrylate resins useful in the practice of the invention may be accomplished by any of the well known polymerization techniques.
The styrene-acrylonitrile and acrylonitrile-butadiene-styrene resins and their preparation are disclosed, inter alia, in U.S. Pat. Nos. 2,769,804; 2,989,517; 2,739,142; 3,991,136 and 4,387,179, all of which are incorporated herein by reference.
The alkyd resins are disclosed in xe2x80x9cAlkyd Resin Technologyxe2x80x9d, Patton, Interscience Publishers, N.Y., N.Y., 1962, and in U.S. Pat. Nos. 3,102,866; 3,228,787 and 4,511,692, all of which are incorporated herein by reference.
These polymeric materials may optionally contain the conventional and well known fillers and reinforcing materials such as mica, talc and glass fibers.
The polymeric layer or basecoat 20 may be applied onto the surface of the substrate by any of the well known and conventional methods such as dipping, spraying, brushing and in chamber plasma process.
The polymeric layer 20 functions, inter alia, to level the surface of the substrate, cover any scratches or imperfections in the surface and provide a smooth and even surface for the deposition of the chrome layer.
The polymeric layer 20 has a thickness at least effective to level out the surface of the substrate. Generally, this thickness is from about 0.1 mil to about 10 mils, preferably from about 0.2 mil to about 5 mils, and more preferably from about 0.3 mil to about 1.5 mils.
The chrome layer 21 may be deposited on the plastic layer 20 by any of the conventional and well known chrome deposition techniques including vapor deposition such as physical vapor deposition and electroplating techniques. The electroplating techniques along with various chrome plating baths are disclosed in Brassard, xe2x80x9cDecorative Electroplatingxe2x80x94A Process in Transitionxe2x80x9d, Metal Finishing, pp. 105-108, June 1988; Zaki, xe2x80x9cChromium Platingxe2x80x9d, PF Directory, pp. 146-160; and in U.S. Pat. Nos. 4,460,438, 4,234,396 and 4,093,522, all of which are incorporated herein by reference.
Chrome plating baths are well known and commercially available. A typical chrome plating bath contains chromic acid or salts thereof, and catalyst ion such as sulfate or fluoride. The catalyst ions can be provided by sulfuric acid or its salts and fluosilicic acid. The baths may be operated at a temperature of about 112xc2x0-116xc2x0 F. Typically in chrome plating a current density of about 150 amps per square foot, at about five to nine volts is utilized.
Generally, the plating of trivalent chrome is preferred because of environmental considerations.
The vapor deposition of the chrome is conventional and well known in the art and includes techniques such as cathodic arc evaporation (CAE) or sputtering. Sputtering techniques and equipment are disclosed, inter alia, in J. Vossen and W. Kern xe2x80x9cThin film Processes IIxe2x80x9d, Academic Press, 1991; R. Boxman et al, xe2x80x9cHandbook of Vacuum Arc Science and Technologyxe2x80x9d, Noyes Pub., 1995; and U.S. Pat. Nos. 4,162,954 and 4,591,418, all of which are incorporated herein by reference.
Briefly, in the sputtering deposition process a metal (i.e., chrome) target, which is the cathode, and the substrate are placed in a vacuum chamber. The air in the chamber is evacuated to produce vacuum conditions in the chamber. An inert gas, such as Argon, is introduced into the chamber. The gas particles are ionized and are accelerated to the target to dislodge titanium or zirconium atoms. The dislodged target material is then typically deposited as a coating film on the substrate.
In cathodic arc evaporation, an electric arc of typically several hundred amperes is struck on the surface of a metal cathode such as chrome. The arc vaporizes the cathode material, which then condenses on the substrates forming a coating.
The chrome/nickel alloy layer may be deposited on the plastic layer 20 by any of the conventional and well known chrome deposition techniques including vapor deposition such as physical vapor deposition and electroplating techniques. The electroplating techniques along with various chrome/nickel plating baths are disclosed in Brassard, xe2x80x9cDecorative Electroplatingxe2x80x94A Process in Transitionxe2x80x9d, Metal Finishing, June 1988; Zaki, xe2x80x9cChromium Platingxe2x80x9d, PF Directory; and in U.S. Pat. Nos. 4,460,438, 4,234,396 and 4,093,522, all of which are incorporated herein by reference.
Chrome/nickel plating baths are well known, conventional and commercially available. A typical chrome/nickel plating bath contains chromic acid or salts thereof, and catalyst ion such as sulfate or fluoride. The catalyst ions can be provided by sulfuric acid or its salts and fluosilicic acid. The baths also may contain nickel sulfate, nickel chloride and boric acid. These baths can include a number of well known and conventionally used compounds such as leveling agents, brighteners, and the like. The baths may be operated at a temperature of about 112xc2x0-116xc2x0 F. Typically in chrome/nickel plating a current density of about 150 amps per square foot, at about five to nine volts is utilized.
The vapor deposition of the chrome/nickel alloy is conventional and well known in the art and includes techniques such as cathodic arc evaporation (CAE) or sputtering. Sputtering techniques and equipment are disclosed, inter alia, in J. Vossen and W. Kern xe2x80x9cThin film Processes IIxe2x80x9d, Academic Press, 1991; R. Boxman et al, xe2x80x9cHandbook of Vacuum Arc Science and Technologyxe2x80x9d, Noyes Pub., 1995; and U.S. Pat. Nos. 4,162,954 and 4,591,418, all of which are incorporated herein by reference.
Briefly, in the sputtering deposition process a metal (i.e., chrome/nickel alloy) target, which is the cathode, and the substrate are placed in a vacuum chamber. The air in the chamber is evacuated to produce vacuum conditions in the chamber. An inert gas, such as Argon, is introduced into the chamber. The gas particles are ionized and are accelerated to the target to dislodge chrome and nickel atoms. The dislodged target materials is then typically deposited as a coating film on the substrate.
In cathodic arc evaporation, an electric arc of typically several hundred amperes is struck on the surface of a metal cathode such as chrome/nickel alloy. The arc vaporizes the cathode material, which then condenses on the substrates forming a coating.
The chrome/nickel alloy which comprises layer 21 generally contains, in percent by weight, from about 5% to about 95% nickel and from about 95% to about 5% chrome, preferably from about 50% to about 90% nickel and from about 10% to about 50% chrome, and more preferably from about 70% to about 90% nickel and from about 10% to about 30% chrome.
The thickness of the chrome or chrome/nickel alloy layer 21 is at least a thickness effective to provide a protective layer and a decorative appearance to the article. Generally this thickness is from about 200 Angstroms to about 35 microns, preferably from about 2,000 Angstroms to about 5,000 Angstroms.
By protective is meant protection of the underlying substrate against corrosion, abrasion, scratching and the like.
In another embodiment layer 21 is comprised of chromium nitride. The chromium nitride layer has the appearance of dark chrome and is deposited by vapor deposition in the presence of nitrogen. The physical vapor deposition processes include reactive sputtering and reactive cathodic arc deposition. Reactive cathodic arc evaporation and reactive sputtering are generally similar to ordinary sputtering and cathodic arc evaporation except that a reactive gas, in this case nitrogen, is introduced into the chamber which reacts with the dislodged target material. Thus, the cathode is comprised of chrome and nitrogen is the reactive gas introduced into the chamber.
The chromium nitride containing layer 21 is generally of the same thickness as the chrome and chrome/nickel alloy layer described supra.